MODELING SYSTEMS FOR SEDIMENT MANAGEMENT AND BMP EVALUATION IN LARGE GREAT LAKES TRIBUTARY WATERSHEDS

Abstract: The identification of water and sediment sources, pathways and sinks is vital to sustainable management of watersheds worldwide. Numerical modeling approaches have been implemented to evaluate water and sediment movement in several large watersheds tributary to Lake Michigan. Numerical models of watershed hydrology and sediment delivery are valuable tools to assist in the planning of Best Management Practices (BMPs) for watershed sediment issues. The models aid in developing a general understanding of the hydrologic and geomorphic behavior of watershed systems, and they allow evaluation and prediction of the effects of changing land use and BMPs such as riparian buffer zone modification. The semi-lumped parameter Soil and Water Assessment Tool (SWAT; USDA-ARS) has been applied on several Great Lakes watersheds to assess historic land use change at the watershed scale. SWAT is particularly suited to simulations on large watersheds over long periods of time. The two-dimensional, finite-difference, Gridded Surface-Subsurface Hydrologic Analysis model (GSSHA; USACE-CHL) was used to evaluate hydrologic and sediment transport processes in detail on subwatersheds nested within the domains of the SWAT model. Because of their detail, the GSSHA model simulations were limited to smaller areas and shorter time simulations. GSSHA allowed for detailed appraisal of modification to buffer strip morphology (such as different vegetation types and strip widths) on different land uses and crop types. A key feature of these studies was the synthesis of the different modeling activities into a single methodology that may be used for watershed management initiatives